PLATE I 



A SERIES OF STAGES IN THE DIFFERENTIATION OF THE TESTIS OF 



BDELLOSTOMA BURGERl 



Fig. 1. Youngest male; testis scarcely differentiated. 



Fig. 2. Slightly older male; testis more distinct. Mesorchium slightly waved in posterior part. 



Fig. 3. Somewhat older than the preceding; follicles can be seen in the testis, which is larger and 



more waved. 

 Fig. 4. Testis band broad, thick, and much folded; follicles more evident. 

 Fig. 5. An adult specimen. Testis increased in width and breadth, and very much folded and 



lobulated. 



All the figures on this plate are one-sixth smaller than the original drawings. 



